Buttonhole stitching attachment



y 31, G. MINKOWI' I'Z BUTTONHOLE STITCHING ATTACHMENT Filed Aug. 15,1937 L In" VINVENTOR @Z M R ATTORNEY Patented May 31, 1938 UNITED STATESPATENT OFFICE 1 Claim.

This invention relates to an intermittent rotary drive attachment forthe feed wheel of a buttonhole sewing machine to provide for a maximumnumber of stitches and to insure an even distribution of the same in themaking of buttonholes.

The present invention is particularly applicable to buttonhole sewingmachines of the older types, e. g., such a machine as is illustrated inUnited States Letters Patent, No. 885,310, of which there are manythousands still in use.

Briefly, in the old type model no provision was made to govern the evendistribution or spacing of stitches used in the forming of buttonholes.The unsatisfactory results obtained in these machines led eventually tothe development of a new button hole machine illustrated in UnitedStates Letters Patent, No. 1,559,539. However, although the new machineswere highly efficient for the purpose for which they were designed,still no provision was made to put the large number of old machines intosatisfactory workable condition. This situation soon led to theconstruction of an attachment for these obsolete machines, which wasapplied to the feed wheel, and which consisted primarily of a slipclutcharrangement operated by the reciprocating arm formerly used to advancethe feed wheel. The slip clutch members were relied upon to frictionallygrip the feed wheel in one direction of movement and to disengage fromthe latter and to move back again in the opposite direction. While thisdevice was an improvement over the original feed wheel drive it did notcompare in efficiency with the positive drive adopted in the machine ofpatent, No. 1,559,539. The disadvantages of the slip clutch were manyand among the most important, was the failure of the slip dogs to takehold and turn the feed wheel during their very slight movement, themovement being governed by the spacing between adjacent stitches formingthe buttonhole. This, it is submitted, was due to the fact that oiloften collected upon the wheel and if not removed it simply caused theclutch dogs to slip in both directions of their movement over the wheelwith the result that the latter failed to be rotated at all.

Thus, the old machines again became useless and a glut upon the marketuntil the conception of the present invention, which has for its objectto provide an attachment for the feed wheel of button hole sewingmachines, which without altering the original machines in any Way isattachable to the feed wheel thereof, and which is capable of impartingto it and its shaft a positive intermittent rotary movement of anypractical degree, no matter how small.

Inasmuch as it was contemplated to utilize the original feed wheel ofthe machine, means had to be devised to accommodate the attachment tothe wheel and at the same time provide for a maximum number ofintermittent movements being imparted thereto, because the maximumnumber of intermittent movements would normally be required to take careof buttonhole stitches, which are made with very fine thread, and whichmust be very closely and evenly spaced from one another.

A further object of this invention, therefore, is to provide a pawl andratchet mechanism in which double pawls are used to alternately engagethe teeth of the ratchet wheel, thereby making it possible tointermittently advance the feed wheel in steps equal to a fraction ofthe distance between ratchet teeth and to correspondingly space andevenly distribute the stitches in the making of a buttonhole.

The objects of this invention have been accomplished by means of adevice, one embodiment of which is hereinafter described in detail, setforth in the appended claim and illustratively exemplified in theaccompanying drawing, in which:

Figure 1 is a bottom plan view of the bed of a button hole sewingmachine, showing the intermittent drive and feed wheel, parts of thedrive being broken away to uncover otherwise hidden parts of themechanism;

Figure 2 is a substantially longitudinal sectional view of the feedwheel and drive taken on line 2-2 of Figure 1; and

Figure 3 is a fragmentary view of the ratchet wheel and double pawltherefor.

Referring to the drawing, l0 denotes the bed plate of a sewing machine,of the buttonhole type represented by Patent No. 885,310, supporting avertical feed shaft II upon the lower end of which the feed wheel I2 issecured. The longitudinal movement of the work holder and associatedparts, not illustrated, are effected by the usual cam slots I3 in theupper face of the feed wheel 12. Mounted in bearings l4 within the bedIll is a rock shaft l5 having a depending arm "5 from which a pitmanconnection I! projects. The other end of the pitman is adjustablymounted by means of a set screw 18 with an arcuately curved slottedswinging arm [9, the arm forming an integral part of an oscillating discplate 20 journalled on the feed shaft ll, beneath the feed cam wheel I2.Movement of the arm I6 imparts an intermittent or step-by-step rotarymovement to the feed wheel I2.

According to the present invention, intermittent movement is imparted tothe feed wheel I2 and shaft ID, by means of an external ratchet wheel2I, which seats against the top wall of a recess in the underside of thefeed wheel I2, and which is provided with a pin 22 adapted to bereceived in an opening 23 drilled in the wall forming the top of therecess. The pin 22 causes the intermittent rotary movement of theratchet to be imparted to the feed wheel I I and shaft Ill. The ratchet2! is provided with an axial hub 24 which fits over the hub of the feedwheel and which forms a bearing for the hub 25 'of the disc plate 20.The assembled parts just described are held in position by means of aset screw 26.

In a mechanical device of this character, where it becomes necessary toimpart a very great number of intermittent rotary movements to anotherpart, the number of individual clutch teeth requires a relatively largecircumference, because each tooth must be suflioiently deep anddistanced far enough from the next tooth to provide ample working spacefor the ratchet engaging pawl. Inasmuch as the feed wheel I2 is a partof the buttonhole machine and must be used, the relatively small workingspace afforded by the wheel requires a special ratchet device whichforms the novel feature of the present invention.

The ratchet wheel 2|, as illustrated, is therefore providedwithapproximately one-half the number of teeth as compared with the maximumnumber of stitches required of the largest buttonhole in order to affordeach tooth with SllffiClBl'lt depth and space to insure engagement by adouble ratchet engaging member. I accomplish the problem of increasingthe number of intermittent rotary movements for one complete rotation ofthe ratchet wheel over the number of teeth contained in its periphery,by dividing each ratchet member into two parts, comprising superimposedpawls 21 and 28, pivotally mounted on a stud shaft 29 carried upright bythe disc plate 20 and yieldably urged at their free ends into engagementwith the teeth of the ratchet wheel by means of springs 30 and 3|, thewidth of the ratchet wheel being equal at least to the width of the twopawls. The inner pawl 21 is slightly shorter than the lower pawl 28 soas to enable one pawl to engage a tooth of the ratchet wheel while theother pawl is held out of engagement with the preceding or followingtooth by approximately one-half the length of the latter. In otherwords, the rocking movement imparted to the arm] I9 may be adjusted soas to require two forward movements thereof to move the ratchet and feedwheel a distance equal to one tooth, thus increasing, and, in fact,doubling, with relation to the number of ratchet teeth, the number ofintermittent rotary movements which may be imparted to the feed wheel II and shaft I to one complete rotation thereof.

In order to insure positive movement of the feed wheel, there are threegroups of double pawls 21--28 arranged in the recess of the wheel I2peripherally of the ratchet wheel 2|, each group being exactly alike andoperating upon the teeth of the ratchet in the same order.

In operation, the shaft I is set in motion and the rocking movement ofthe arm I6 causes the pitman I1 to reciprocate. Adjusted in properrelative position on the arm I9, the pitman I1 sets up an oscillatingrotary movement in the disc plate 20, which carries the three groups ofdouble pawls 21 and 28. As the disc oscillates in the direction of thearrow in Figure 1, the

-longer pawls 21, engaged in the teeth of the ratchet wheel 2I will stepthe latter and feed wheel I2 ahead a distance corresponding to therelative position of the pitman connection with the arm I9 and the axisof the feed shaft II. If adjustment is such as to make the oscillatingmovement very short, 1. e. a minimum distance equal to one-half thedistance between ratchet teeth, then the lower or shorter pawls 28 willengage the next teeth and the longer pawls 21 will rest on the upperslopes of the adjacent teeth and during the next movement ahead of thearm I9 and plate 20 the shorter pawls 28 will take their turn atstepping the ratchet wheel 2| and feed wheel I2 ahead. Thus, it ispossible to at least double the number of intermittent rotary movementsimparted to a ratchet wheel over the number of ratchet teeth thereof.With the greatly increased number of positively spaced intermittentrotary movements, taken by the feed wheel I2 and shaft I I, according tothe present invention, the greater will be the number and distributionof buttonhole stitches which may be I efiected in the making ofbuttonholes.

What is claimed as new is:

In a buttonhole stitching attachment a driving mechanism forintermittently rotating a shaft comprising a driven disc fixed on saidshaft, said disc having a hub portion projecting axially to the end ofthe shaft and an integral axially projecting circumferential flange, aratchet wheel of a diameter smaller than the inner diameter of saidflange, disposed within said 1 flange on the hub of said driven disc andrigidly connected with the latter, said ratchet wheel having a hubportion projecting beyond the hub of the driven disc and the end of theshaft and being internally threaded, an oscillating carrier disc of adiameter exceeding the inner diameter of said flange and being rotatablyarranged on the projecting hub portion of said ratchet wheel, saidoscillating disc carrying circumferentially spaced pawls yieldablyengaging the teeth of said ratchet wheel to impart thereto and to thedriven member an intermittent rotary movement in one direction, and. aset screw having a head overlapping the bore of said carrier disc andbeing screwed into said threaded hub portion of the ratchet wheel tohold said carrier disc in contact with said flange whereby said pawl andratchet mechanism is tightly enclosed in a casing formed by the carrierdisc, the driven disc and the circumferential flange of the latter.

' GEORGE MINKOWITZ.

